I have wanted this and suggested it before for use with typing.
Defining protocols is obnoxiously verbose for "struct" like data and
keyword
arguments to subscript could help alleviate that.
I often want to write type hint like this:
```
def foo(x: Protocol[id=int, name=str]):
bar(x)
baz(x)
def bar(x: Protocol[name=str]): ...
def baz(x: Protocol[id=int]): ...
```
So I either need to specify more restrictive types than necessary (which
often
is not possible because I reuse my functions), or generate a combinatorial
number of Protocols. Beyond the obvious annoyances that come with having
to
generate many protocols, simply naming them is cognitively expensive. I
don't
need to bind an identifier when declaring a Union or specializing a generic
but
if I want to say I have a type with some attribute it MUST be named.
On Fri, Jul 10, 2020 at 10:00 AM Paul Moore <p.f.mo...@gmail.com> wrote:
> On Fri, 10 Jul 2020 at 17:45, Steven D'Aprano <st...@pearwood.info> wrote:
>
> > I must admit I like the look of this, but I don't know what I would use
> > it for.
>
> It feels very much like the sort of "here's some syntax that might
> match someone's mental model of something" that is common in languages
> that focus on allowing users to build their own DSLs¹ (Lua and Groovy
> are two examples of the type of language I'm thinking of, although I
> don't know if either has this particular syntax).
>
> Python typically doesn't encourage DSL-style programming, so this type
> of "syntax looking for a use case" isn't very popular.
>
> Paul
>
> ¹ DSL = Domain Specific Language, in case anyone isn't familiar with the
> term.
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